U.S. Pat. No. 4,147,073 discloses a reversible motor that drives a main screw to rotate reversibly and drive a nut slider to move axially. The slider is connected to a garage door. A second screw is coaxially connected to the main screw and the screw-pitch thereof is small. The switch actuator on the second screw only moves axially to make the garage door move up and down (ie open and close).
U.S. Pat. No. 5,299,678 discloses an adjustable limit switch mechanism to control the operation of the electric motor of a garage door opener to make the garage door move in a selected range. The switch mechanism comprises a screw driven by the electric motor and at least one switch actuator disposed on the screw which is adjustably positionable. When the screw rotates, the switch actuator does not rotate with the screw and moves only axially. A limit switch is adjacent to the screw so that when the screw rotates, the switch actuator moves axially on the screw to actuate the limit switch thereby causing the motor to operate or stop. These two switch mechanisms are remotely disposed at the respective ends of the screw so that the range of movement is difficult to adjust. Furthermore, the two switch mechanisms are linear and cannot directly control the range of movement of the screw.